Rotating control head radial seal protection and leak detection systems

ABSTRACT

A system and method for reducing repairs to radial seals used in a rotating control head used while drilling is disclosed. Also, a system and method to detect leaks in the rotating control head and a latching system to latch the rotating control head to a housing is disclosed.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of U.S. application Ser. No.10/285,336 entitled “Active/Passive Seal Rotating Control Head” filedOct. 31, 2002, and U.S. application Ser. No. 10/995,980 entitled “RiserRotating Control Device” filed Nov. 23, 2004, both of which areincorporated by reference in their entirety for all purposes.

STATEMENTS REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not applicable.

REFERENCE TO A MICROFICHE APPENDIX

Not applicable.

BACKGROUND OF THE INVENTION

1. Field of the Invention

Embodiments of the present invention relate generally to a method and asystem for a rotating control head used in a drilling operation. Moreparticularly, the invention relates to a remote leak detection system,radial seal protection system and an improved cooling system for arotating control head and a method for using the systems. The presentinvention also includes a leak detection system for a latch system tolatch the rotating control device to a housing.

2. Description of the Related Art

Drilling a wellbore for hydrocarbons requires significant expendituresof manpower and equipment. Thus, constant advances are being sought toreduce any downtime of equipment and expedite any repairs that becomenecessary. Rotating equipment requires maintenance as the drillingenvironment produces forces, elevated temperatures and abrasive cuttingsdetrimental to the longevity of seals, bearings, and packing elements.

In a typical drilling operation, a drill bit is attached to a drillpipe. Thereafter, a drive unit rotates the drill pipe through a drivemember, referred to as a kelly as the drill pipe and drill bit are urgeddownward to form the wellbore. In some arrangements, a kelly is notused, thereby allowing the drive unit to attach directly to the drillpipe or tubular. The length of the wellbore is determined by thelocation of the hydrocarbon formations. In many instances, theformations produce fluid pressure that may be a hazard to the drillingcrew and equipment unless properly controlled.

Several components are used to control the fluid pressure. Typically,one or more blowout preventers (BOP) are mounted with the well forming aBOP stack to seal the well. In particular, an annular BOP is used toselectively seal the lower portions of the well from a tubular thatallows the discharge of mud. In many instances, a conventional rotatingcontrol head is mounted above the BOP stack. An inner portion or memberof the conventional rotating control head is designed to seal and rotatewith the drill pipe. The inner portion or member typically includes atleast one internal sealing element mounted with a plurality of bearingsin the rotating control head.

The internal sealing element may consist of either one, two or both of apassive seal assembly and/or an active seal assembly. The active sealassembly can be hydraulically or mechanically activated. Generally, ahydraulic circuit provides hydraulic fluid to the active seal in therotating control head. The hydraulic circuit typically includes areservoir containing a supply of hydraulic fluid and a pump tocommunicate the hydraulic fluid from the reservoir to the rotatingcontrol head. As the hydraulic fluid enters the rotating control head, apressure is created to energize the active seal assembly. Preferably,the pressure in the active seal assembly is maintained at a greaterpressure than the wellbore pressure. Typically, the hydraulic circuitreceives input from the wellbore and supplies hydraulic fluid to theactive seal assembly to maintain the desired pressure differential.

During the drilling operation, the drill pipe or tubular is axially andslidably moved through the rotating control head. The axial movement ofthe drill pipe along with other forces experienced in the drillingoperation, some of which are discussed below, causes wear and tear onthe bearing and seal assembly and the assembly subsequently requiresrepair. Typically, the drill pipe or a portion thereof is pulled fromthe well and the bearing and seal assembly in the rotating control headis then released. Thereafter, an air tugger or other lifting means incombination with a tool joint on the drill string can be used to liftthe bearing and seal assembly from the rotating control head. Thebearing and seal assembly is replaced or reworked, the bearing and sealassembly installed into the rotating control head, and the drillingoperation is resumed.

The thrust generated by the wellbore fluid pressure, the radial forceson the bearing assembly and other forces cause a substantial amount ofheat to build in the conventional rotating control head. The heat causesthe seals and bearings to wear and subsequently require repair. Theconventional rotating control head typically includes a cooling systemthat circulates fluid through the seals and bearings to remove the heat.

Cooling systems have been known in the past for rotating control headsand rotating blowout preventers. For example, U.S. Pat. Nos. 5,178,215,5,224,557 and 5,277,249 propose a heat exchanger for cooling hydraulicfluid to reduce the internal temperature of a rotary blowout preventerto extend the operating life of various bearing and seal assembliesfound therein.

FIG. 10 discloses a system where hydraulic fluid moves through the sealcarrier C of a rotating control head, generally indicated at RCH, in asingle pass to cool top radial seals S1 and S2 but with the fluidexternal to the bearing section B. Similarly, U.S. Pat. No. 5,662,181,assigned to the assignee of the present invention, discloses use offirst inlet and outlet fittings for circulating a fluid, i.e. chilledwater and/or antifreeze, to cool top radial seals in a rotating controlhead. A second lubricant inlet fitting is used for supplying fluid forlubricating not only the top radial seals but also top radial bearings,thrust bearings, bottom radial bearings and bottom radial seals allpositioned beneath the top radial seals. (See '181 patent, col. 5, In.42 to col. 6, In. 10 and col. 7, Ins. 1-10.) These two separate fluidsrequire their own fluid flow equipment, including hydraulic/pneumatichoses.

Also, U.S. Pat. No. 5,348,107 proposes means for circulating lubricantaround and through the interior of a drilling head. More particularly,FIGS. 3 to 6 of the '107 patent propose circulating lubricant to sealsvia a plurality of passageways in the packing gland. These packing glandpassageways are proposed to be in fluid communication with the lubricantpassageways such that lubricant will freely circulate to the seals. (See'107 patent, col. 3, Ins. 27-65.)

U.S. Pat. Nos. 6,554,016 and 6,749,172, assigned to the assignee of thepresent invention, propose a rotary blowout preventer with a first and asecond fluid lubricating, cooling and filtering circuit separated by aseal. Adjustable orifices are proposed connected to the outlet of thefirst and second fluid circuits to control pressures within thecircuits. Such pressures are stated to affect the wear rates of theseals and to control the wear rate of one seal relative to another seal.

Therefore, an improved system for cooling radial seals and the bearingsection of a rotating control head with one fluid is desired. If theradial seals are not sufficiently cooled, the localized temperature atthe sealing surface will rise until the temperature limitations of theseal material is reached and degradation of the radial seal begins. Thefaster the rise in temperature means less life for the radial seals. Inorder to obtain sufficient life from radial seals, the rate of heatextraction should be fast enough to allow the temperature at the sealingsurface to level off at a temperature lower than that of the sealmaterial's upper limit.

Also, to protect the radial seals in a rotating control head, it wouldbe desirable to regulate the differential pressure across the upper topradial seal that separates the fluid from the environment. Typically,fluid pressure is approximately 200 psi above the wellbore pressure.This pressure is the differential pressure across the upper top radialseal. Radial seals have a PV factor, which is differential pressureacross the seal times the rotary velocity of the inner portion or memberof the rotating control head in surface feet per minute. When this valueis exceeded, the radial seal fails prematurely. Thus, the PV factor isthe limitation to the amount of pressure and RPM that a rotating controlhead can be expected to perform. When the PV factor is exceeded, eitherexcessive heat is generated by friction of the radial seals on therotating inner member, which causes the seal material to break down, orthe pressure forces the radial seal into the annular area between therotating inner member and stationary outer member which damages thedeformed seal.

In general, this PV seal problem has been addressed by limiting the RPM,pressure or both in a rotating control head. The highest dynamic, butrarely experienced, rating on a rotating control head is presentlyapproximately 2500 psi. Some companies publish life expectancy chartswhich will provide the expected life of a radial seal for a particularpressure and RPM value. An annular labyrinth ring has also been used inthe past between the lubricant and top radial seal to reduce thedifferential pressure across the top radial seal. Pressure staging andcooling of seals has been proposed in U.S. Pat. No. 6,227,547, assignedon its face to Kalsi Engineering, Inc. of Sugar Land, Tex.

Furthermore, U.S. Ser. No. 10/995,980 discloses in FIG. 14 a remotecontrol display 1400 having a hydraulic fluid indicator 1488 to indicatea fluid leak condition. FIG. 18 of the '980 application furtherdiscloses that the alarm indicator 1480 and horn are activated based inpart on the fluid leak indicator 1488 being activated for apredetermined time.

The above discussed U.S. Pat. Nos. 5,178,215; 5,224,557; 5,277,249;5,348,107; 5,662,181; 6,227,547; 6,554,016; and 6,749,172 areincorporated herein by reference in their entirety for all purposes.

There is a need therefore, for an improved, cost-effective rotatingcontrol head that reduces repairs to the seals in the rotating controlhead and an improved leak detection system to indicate leaks pass theseseals. There is a further need for a cooling system in a rotatingcontrol head for top radial seals that can be easily implemented andmaintained. There is yet a further need for an improved rotating controlhead where the PV factor is reduced by regulating the differentialpressure across the upper top radial seal. There is yet a further needfor an improved leak detection system for the rotating control head andits latching system.

BRIEF SUMMARY OF THE INVENTION

The present invention generally relates to a system and method forreducing repairs to a rotating control head and a system and method todetect leaks in the rotating control head and its latching system.

In particular, the present invention relates to a system and method forcooling a rotating control head while regulating the pressure on theupper top radial seal in the rotating control head to reduce its PVfactor. The improved rotating control head includes an improved coolingsystem using one fluid to cool the radial seals and bearings incombination with a reduced PV factor radial seal protection system.

A leak detection system and method of the present invention uses acomparator to compare fluid values in and from the latch assembly of thelatch system and/or in and from the bearing section or system of therotating control head.

In another aspect, a system and method for sealing a tubular in arotating control head is provided. The method includes supplying fluidto the rotating control head and activating a seal arrangement to sealaround the tubular. The system and method further includes passing acooling medium through the rotating control head while maintaining apressure differential between a fluid pressure in the rotating controlhead and a wellbore pressure.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

So that the manner in which the above recited features of the presentinvention can be understood in detail, a more particular description ofthe invention, briefly summarized above, may be had by reference toembodiments, some of which are illustrated in the appended drawings. Itis to be noted, however, that the appended drawings illustrate onlytypical embodiments of this invention and are therefore not to beconsidered limiting of its scope, for the invention may be used in otherequally effective embodiments.

FIG. 1 is an elevational section view illustrating a rotating controlhead having an active seal assembly positioned above a passive sealassembly latched in a housing in accord with the present invention.

FIG. 2A illustrates a rotating control head cooled by a heat exchanger.

FIG. 2B illustrates a schematic view of the heat exchanger.

FIG. 3A illustrates a rotating control head cooled by flow a gas.

FIG. 3B illustrates a schematic view of the gas in a substantiallycircular passageway.

FIG. 4A illustrates a rotating control head cooled by a fluid mixture.

FIG. 4B illustrates a schematic view of the fluid mixture circulating ina substantially circular passageway.

FIG. 5A illustrates the rotating control head cooled by a refrigerant.

FIG. 5B illustrates a schematic view of the refrigerant circulating in asubstantially circular passageway.

FIG. 6 illustrates a rotating control head actuated by a pistonintensifier in communication with the wellbore pressure.

FIG. 7A illustrates an alternative embodiment of a rotating control headwith a passive seal assembly and an active seal assembly mechanicalannular blowout preventer (BOP) in an unlocked position.

FIG. 7B illustrates the rotating control head of FIG. 7A with theannular BOP in a locked position.

FIG. 8 illustrates an alternative embodiment of a rotating control headwith a passive seal assembly positioned above an active seal assembly inaccord with the present invention.

FIG. 9 is an elevational section view showing a rotating control headwith two passive seal assemblies latched in a housing in accord with thepresent invention.

FIG. 10 is an enlarged section view of a prior art rotating control headsystem where cooling fluid moves through the seal carrier in a singlepass but with the fluid external to the bearing section.

FIG. 11 is an enlarged section view of a rotating control head coolingsystem where air moves through a passageway similar to the passagewayshown in above FIGS. 2A and 2B.

FIG. 12 is an enlarged section view of a rotating control head wherehydraulic fluid moves through the seal carrier to cool the top radialseals in a single pass.

FIG. 13 is an enlarged section view showing staging pressure on radialseals for a rotating control head in accord with the present invention,including regulating pressure between an upper top radial seal and ahigh flow lower top radial seal.

FIG. 14 is an enlarged section view of a multi-pass heat exchanger for arotating control head in accord with the present invention where ahydraulic fluid is both moved through the bearing section and makesmultiple passes around the radial seals.

FIGS. 15A and 15B are schematics of the preferred hydraulic system forthe present invention.

FIG. 16 is a flowchart for operation of the hydraulic system of FIG. 15of the present invention.

FIG. 17 is a continuation of the flowchart of FIG. 16.

FIG. 18 is a continuation of the flowchart of FIG. 17.

FIG. 19 is a flowchart of a subroutine for controlling the pressure inthe bearing section of the rotating control head of the presentinvention.

FIG. 20 is a continuation of the flowchart of FIG. 19.

FIG. 21 is a continuation of the flowchart of FIG. 20.

FIG. 22 is a continuation of the flowchart of FIG. 21.

FIG. 23 is a flowchart of a subroutine for controlling either thepressure of the latching system in the housing, such as shown in FIGS. 1and 9, or the pressure on the radial seals, as shown in FIG. 13, of thepresent invention.

FIG. 24 is a continuation of the flowchart of FIG. 23.

FIG. 25 is a plan view of a control console in accord with the presentinvention.

FIG. 26 is an enlarged elevational section view of a latch assembly inthe latched position with a perpendicular port communicating above apiston indicator valve that is shown in a closed position.

FIG. 27 is a view similar to FIG. 26 but taken at a different sectioncut to show another perpendicular port communicating below the closedpiston indicator valve.

DETAILED DESCRIPTION OF THE INVENTION

Generally, the present invention relates to a rotating control head foruse with a drilling rig. Typically, an inner portion or member of therotating control head is designed to seal around a rotating tubular androtate with the tubular by use of an internal sealing element andbearings. Additionally, the inner portion of the rotating control headpermits the tubular to move axially and slidably through the rotatingcontrol head on the drilling rig.

FIG. 1 is a cross-sectional view illustrating the rotating control head,generally indicated at 100, in accord with the present invention. Therotating control head 100 preferably includes an active seal assembly105 and a passive seal assembly 110. Each seal assembly 105, 110includes components that rotate with respect to a housing 115. Thecomponents that rotate in the rotating control head are mounted forrotation about a plurality of bearings 125.

As depicted, the active seal assembly 105 includes a bladder supporthousing 135 mounted within the plurality of bearings 125. The bladdersupport housing 135 is used to mount bladder 130. Under hydraulicpressure, as discussed below, bladder 130 moves radially inward to sealaround a tubular, such as a drilling pipe or tubular (not shown). Inthis manner, bladder 130 can expand to seal off a borehole using therotating control head 100.

As illustrated in FIG. 1, upper and lower caps 140, 145 fit over therespective upper and lower end of the bladder 130 to secure the bladder130 within the bladder support housing 135. Typically, the upper andlower caps 140, 145 are secured in position by a setscrew (not shown).Upper and lower seals 155, 160 seal off chamber 150 that is preferablydefined radially outwardly of bladder 130 and radially inwardly ofbladder support housing 135.

Generally, fluid is supplied to the chamber 150 under a controlledpressure to energize the bladder 130. A hydraulic control will beillustrated and discussed in FIGS. 2-6. Essentially, the hydrauliccontrol maintains and monitors hydraulic pressure within pressurechamber 150. Hydraulic pressure P1 is preferably maintained by thehydraulic control between 0 to 200 psi above a wellbore pressure P2. Thebladder 130 is constructed from flexible material allowing bladdersurface 175 to press against the tubular at approximately the samepressure as the hydraulic pressure P1. Due to the flexibility of thebladder, it also may conveniently seal around irregular shaped tubularstring, such as a hexagonal kelly. In this respect, the hydrauliccontrol maintains the differential pressure between the pressure chamber150 at pressure P1 and wellbore pressure P2. Additionally, the activeseal assembly 105 includes support fingers 180 to support the bladder130 at the most stressful area of the seal between the fluid pressure P1and the ambient pressure.

The hydraulic control may be used to de-energize the bladder 130 andallow the active seal assembly 105 to release the seal around thetubular. Generally, fluid in the chamber 150 is drained into a hydraulicreservoir (not shown), thereby reducing the pressure P1. Subsequently,the bladder surface 175 loses contact with the tubular as the bladder130 becomes de-energized and moves radially outward. In this manner, theseal around the tubular is released allowing the tubular to be removedfrom the rotating control head 100.

In the embodiment shown in FIG. 1, the passive seal assembly 110 isoperatively attached to the bladder support housing 135, therebyallowing the passive seal assembly 110 to rotate with the active sealassembly 105. Fluid is not required to operate the passive seal assembly110 but rather it utilizes pressure P2 to create a seal around thetubular. The passive seal assembly 110 is constructed and arranged in anaxially downward conical shape, thereby allowing the pressure P2 to actagainst a tapered surface 195 to close the passive seal assembly 110around the tubular. Additionally, the passive seal assembly 110 includesan inner diameter 190 smaller than the outer diameter of the tubular toprovide an interference fit between the tubular and the passive sealassembly 110.

FIG. 2A illustrates a rotating control head 200 cooled by heat exchanger205. As shown, the rotating control head 200 is depicted generally toillustrate this embodiment of the invention, thereby applying thisembodiment to a variety of different types of rotating control heads. Ahydraulic control 210 provides fluid to the rotating control head 200.The hydraulic control 210 typically includes a reservoir 215 to containa supply of fluid, a pump 220 to communicate the fluid from thereservoir 215 to the rotating control head 200 and a valve 225 to removeexcess pressure in the rotating control head 200.

Generally, the hydraulic control 210 provides fluid to energize abladder 230 and lubricate a plurality of bearings 255. As the fluidenters a port 235, the fluid is communicated to the plurality ofbearings 255 and a chamber 240. As the chamber 240 fills with a fluid,pressure P1 is created. The pressure P1 acts against the bladder 230causing the bladder 230 to expand radially inward to seal around atubular string (not shown). Typically, the pressure P1 is maintainedbetween 0-200 psi above a wellbore pressure P2.

The rotating control head 200 is cooled by the heat exchanger 205. Theheat exchanger 205 is constructed and arranged to remove heat from therotating control head 200 by introducing a gas, such as air, at a lowtemperature into an inlet 265 and thereafter transferring heat energyfrom a plurality of radial seals 275A and 275B and the plurality ofbearings 255 to the gas as the gas passes through the heat exchanger205. Subsequently, the gas at a higher temperature exits the heatexchanger 205 through an outlet 270. Typically, gas is pumped into theinlet 265 by a blowing apparatus (not shown). However, other means ofcommunicating gas to the inlet 265 may be employed, so long as they arecapable of supplying a sufficient amount of gas to the heat exchanger205.

FIG. 2B illustrates a schematic view of the heat exchanger 205. Asillustrated, the heat exchanger 205 comprises a passageway 280 with aplurality of substantially square curves. The passageway 280 is arrangedto maximize the surface area covered by the heat exchanger 205. The lowtemperature gas entering the inlet 265 flows through the passageway 280in the direction illustrated by arrow 285. As the gas circulates throughthe passageway 280, the gas increases in temperature as the heat fromthe rotating control head 200 is transferred to the gas. The hightemperature gas exits the outlet 270 as indicated by the direction ofarrow 285. In this manner, the heat generated by the rotating controlhead 200 is transferred to the gas passing through the heat exchanger205.

FIG. 3A illustrates a rotating control head 300 cooled by a gas. Asshown, the rotating control head 300 is depicted generally to illustratethis embodiment of the invention, thereby applying this embodiment to avariety of different types of rotating control heads. A hydrauliccontrol 310 supplies fluid to the rotating control head 300. Thehydraulic control 310 typically includes a reservoir 315 to contain asupply of fluid and a pump 320 to communicate the fluid from thereservoir 315 to the rotating control head 300. Additionally, thehydraulic control 310 includes a valve 345 to relieve excess pressure inthe rotating control head 300.

Generally, the hydraulic control 310 supplies fluid to energize abladder 330 and lubricate a plurality of bearings 355. As the fluidenters a port 335, a portion is communicated to the plurality ofbearings 355 and another portion is used to fill a chamber 340. As thechamber 340 fills with a fluid, a pressure P1 is created. Pressure P1acts against the bladder 330 causing the bladder 330 to move radiallyinward to seal around a tubular (not shown). Typically, the pressure P1is maintained between 0 to 200 psi above a wellbore pressure P2. If thewellbore pressure P2 drops, the pressure P1 may be relieved throughvalve 345 by removing a portion of the fluid from the chamber 340.

The rotating control head 300 is cooled by a flow of gas through asubstantially circular passageway 380 through an upper portion of therotating control head 300. The circular passageway 380 is constructedand arranged to remove heat from the rotating control head 300 byintroducing a gas, such as air, at a low temperature into an inlet 365,transferring heat energy to the gas and subsequently allowing the gas ata high temperature to exit through an outlet 370. The heat energy istransferred from a plurality of radial seals 375A and 375B and theplurality of bearings 355 as the gas passes through the circularpassageway 380. Typically, gas is pumped into the inlet 365 by a blowingapparatus (not shown). However, other means of communicating gas to theinlet 365 may be employed, so long as they are capable of supplying asufficient amount of gas to the substantially circular passageway 380.

FIG. 3B illustrates a schematic view of the gas passing through thesubstantially circular passageway 380. The circular passageway 380 isarranged to maximize the surface area covered by the circular passageway380. The low temperature gas entering the inlet 365 flows through thecircular passageway 380 in the direction illustrated by arrow 385. Asthe gas circulates through the circular passageway 380, the gasincreases in temperature as the heat from the rotating control head 300is transferred to the gas. The high temperature gas exits the outlet 370as indicated by the direction of arrow 385. In this manner, the heatgenerated by the rotating control head 300 is removed allowing therotating control head 300 to function properly.

In an alternative embodiment, the rotating control head 300 may operatewithout the use of the circular passageway 380. In other words, therotating control head 300 would function properly without removing heatfrom the plurality of radial seals 375A and 375B and the plurality ofbearings 355. This alternative embodiment typically applies when thewellbore pressure P2 is relatively low.

FIGS. 4A and 4B illustrate a rotating control head 400 cooled by a fluidmixture. As shown, the rotating control head 400 is depicted generallyto illustrate this embodiment of the invention, thereby applying thisembodiment to a variety of different types of rotating control heads. Ahydraulic control 410 supplies fluid to the rotating control head 400.The hydraulic control 410 typically includes a reservoir 415 to containa supply of fluid and a pump 420 to communicate the fluid from thereservoir 415 to the rotating control head 400. Additionally, thehydraulic control 410 includes a valve 445 to relieve excess pressure inthe rotating control head 400. In the same manner as the hydrauliccontrol 310, the hydraulic control 410 supplies fluid to energize abladder 430 and lubricate a plurality of bearings 455.

The rotating control head 400 is cooled by a fluid mixture circulatedthrough a substantially circular passageway 480 on an upper portion ofthe rotating control head 400. In the embodiment shown, the fluidmixture preferably consists of water or a water-glycol mixture. However,other mixtures of fluid may be employed, so long as, the fluid mixturehas the capability to circulate through the circular passageway 480 andreduce the heat in the rotating control head 400.

The circular passageway 480 is constructed and arranged to remove heatfrom the rotating control head 400 by introducing the fluid mixture at alow temperature into an inlet 465, transferring heat energy to the fluidmixture and subsequently allowing the fluid mixture at a hightemperature to exit through an outlet 470. The heat energy istransferred from a plurality of radial seals 475A and 475B and theplurality of bearings 455 as the fluid mixture circulates through thecircular passageway 480. The fluid mixture is preferably pumped into theinlet 465 through a fluid circuit 425. The fluid circuit 425 iscomprised of a reservoir 490 to contain a supply of the fluid mixtureand a pump 495 to circulate the fluid mixture through the rotatingcontrol head 400.

FIG. 4B illustrates a schematic view of the fluid mixture circulating inthe substantially circular passageway 480. The circular passageway 480is arranged to maximize the surface area covered by the circularpassageway 480. The low temperature fluid entering the inlet 465 flowsthrough the circular passageway 480 in the direction illustrated byarrow 485. As the fluid circulates through the circular passageway 480,the fluid increases in temperature as the heat from the rotating controlhead 400 is transferred to the fluid. The high temperature fluid exitsout the outlet 470 as indicated by the direction of arrow 485. In thismanner, the heat generated by the rotating control head 400 is removedallowing the rotating control head 400 to function properly.

FIGS. 5A and 5B illustrate a rotating control head 500 cooled by arefrigerant. As shown, the rotating control head 500 is depictedgenerally to illustrate this embodiment of the invention, therebyapplying this embodiment to a variety of different types of rotatingcontrol heads. A hydraulic control 510 supplies fluid to the rotatingcontrol head 500. The hydraulic control 510 typically includes areservoir 515 to contain a supply of fluid and a pump 520 to communicatethe fluid from the reservoir 515 to the rotating control head 500.Additionally, the hydraulic control 510 includes a valve 545 to relieveexcess pressure in the rotating control head 500. In the same manner asthe hydraulic control 310, the hydraulic control 510 supplies fluid toenergize a bladder 530 and lubricate a plurality of bearings 555.

The rotating control head 500 is cooled by a refrigerant circulatedthrough a substantially circular passageway 580 in an upper portion ofthe rotating control head 500. The circular passageway 580 isconstructed and arranged to remove heat from the rotating control head500 by introducing the refrigerant at a low temperature into an inlet565, transferring heat energy to the refrigerant and subsequentlyallowing the refrigerant at a high temperature to exit through an outlet570. The heat energy is transferred from a plurality of radial seals575A and 575B and the plurality of bearings 555 as the refrigerantcirculates through the circular passageway 580. The refrigerant ispreferably communicated into the inlet 565 through a refrigerant circuit525. The refrigerant circuit 525 includes a reservoir 590 containing asupply of vapor refrigerant. A compressor 595 draws the vaporrefrigerant from the reservoir 590 and compresses the vapor refrigerantinto a liquid refrigerant. Thereafter, the liquid refrigerant iscommunicated to an expansion valve 560. At this point, the expansionvalve 560 changes the low temperature liquid refrigerant into a lowtemperature vapor refrigerant as the refrigerant enters inlet 565.

FIG. 5B illustrates a schematic view of the vapor refrigerantcirculating in the substantially circular passageway 580. The circularpassageway 580 is arranged in an approximately 320-degree arc tomaximize the surface area covered by the circular passageway 580. Thelow temperature vapor refrigerant entering the inlet 565 flows throughthe circular passageway 580 in the direction illustrated by arrow 585.As the vapor refrigerant circulates through the circular passageway 580,the vapor refrigerant increases in temperature as the heat from therotating control head 500 is transferred to the vapor refrigerant. Thehigh temperature vapor refrigerant exits out the outlet 570 as indicatedby the direction of arrow 585. Thereafter, the high temperature vaporrefrigerant rejects the heat to the environment through a heat exchanger(not shown) and returns to the reservoir 590. In this manner, the heatgenerated by the rotating control head 500 is removed allowing therotating control head 500 to function properly.

FIG. 6 illustrates a rotating control head 600 actuated by a pistonintensifier circuit 610 in communication with a wellbore 680. As shown,the rotating control head 600 is depicted generally to illustrate thisembodiment of the invention, thereby applying this embodiment to avariety of different types of rotating control heads. The pistonintensifier circuit 610 supplies fluid to the rotating control head 600.The piston intensifier circuit 610 typically includes a housing 645 anda piston arrangement 630. The piston arrangement, generally indicated at630, is formed from a larger piston 620 and a smaller piston 615. Thepistons 615, 620 are constructed and arranged to maintain a pressuredifferential between a hydraulic pressure P1 and a wellbore pressure P2.In other words, the pistons 615, 620 are designed with a specificsurface area ratio to maintain about a 200 psi pressure differentialbetween the hydraulic pressure P1 and the wellbore pressure P2, therebyallowing the P1 to be 200 psi higher than P2. The piston arrangement 630is disposed in the housing 645 to form an upper chamber 660 and lowerchamber 685. Additionally, a plurality of seal members 605, 606 aredisposed around the pistons 615, 620, respectively, to form a fluidtight seal between the chambers 660, 685.

The piston intensifier circuit 610 mechanically provides hydraulicpressure P1 to energize a bladder 650. Initially, fluid is filled intoupper chamber 660 and is thereafter sealed. The wellbore fluid from thewellbore 680 is in fluid communication with lower chamber 685.Therefore, as the wellbore pressure P2 increases more wellbore fluid iscommunicated to the lower chamber 685 creating a pressure in the lowerchamber 685. The pressure in the lower chamber 685 causes the pistonarrangement 630 to move axially upward forcing fluid in the upperchamber 660 to enter port 635 and pressurize a chamber 640. As thechamber 640 fills with a fluid, the pressure P1 increases causing thebladder 650 to move radially inward to seal around a tubular (notshown). In this manner, the bladder 650 is energized allowing therotating control head 600 to seal around a tubular.

A fluid, such as water-glycol, is circulated through the rotatingcontrol head 600 by a fluid circuit 625. Typically, heat on the rotatingcontrol head 600 is removed by introducing the fluid at a lowtemperature into an inlet 665, transferring heat energy to the fluid andsubsequently allowing the fluid at a high temperature to exit through anoutlet 670. The heat energy is transferred from a plurality of radialseals 675A and 675B and the plurality of bearings 655 as the fluidcirculates through the rotating control head 600. The fluid ispreferably pumped into the inlet 665 through the fluid circuit 625.Generally, the circuit 625 comprises a reservoir 690 to contain a supplyof the fluid and a pump 695 to circulate the fluid through the rotatingcontrol head 600.

In another embodiment, the piston intensifier circuit 610 is in fluidcommunication with a nitrogen gas source (not shown). In thisembodiment, a pressure transducer (not shown) measures the wellborepressure P2 and subsequently injects nitrogen into the lower chamber 685at the same pressure as pressure P2. The nitrogen pressure in the lowerchamber 685 may be adjusted as the wellbore pressure P2 changes, therebymaintaining the desired pressure differential between hydraulic pressureP1 and wellbore pressure P2.

FIG. 7A illustrates an alternative embodiment of a rotating control head700 in an unlocked position. The rotating control head 700 is arrangedand constructed in a similar manner as the rotating control head 100shown on FIG. 1. Therefore, for convenience, similar components thatfunction in the same manner will be labeled with the same numbers as therotating control head 100. The primary difference between the rotatingcontrol head 700 and rotating control head 100 is the active sealassembly.

As shown in FIG. 7A, the rotating control head 700 includes an activeseal assembly, generally indicated at 705. The active seal assembly 705includes a primary seal 735 that moves radially inward as a piston 715wedges against a tapered surface of the seal 735. The primary seal 735is constructed from flexible material to permit sealing aroundirregularly shaped tubular string such as a hexagonal kelly. The upperend of the seal 735 is connected to a top ring 710.

The active sealing assembly 705 includes an upper chamber 720 and alower chamber 725. The upper chamber 720 is formed between the piston715 and a piston housing 740. To move the rotating control head 700 froman unlocked or relaxed position to a locked or sealed position, fluid ispumped through port 745 into an upper chamber 720. As fluid fills theupper chamber 720, the pressure created acts against the lower end ofthe piston 715 and urges the piston 715 axially upward towards the topring 710. At the same time, the piston 715 wedges against the taperedportion of the primary seal 735 causing the seal 735 to move radiallyinward to seal against the tubular (not shown). In this manner, theactive seal assembly 705 is in the locked or sealed position asillustrated in FIG. 7B.

As shown on FIG. 7B, the piston 715 has moved axially upward contactingthe top ring 710 and the primary seal 735 has moved radially inward. Tomove the active seal assembly 705 from the locked position to theunlocked position, fluid is pumped through port 755 into the lowerchamber 725. As the chamber fills up, the fluid creates a pressure thatacts against surface 760 to urge the piston 715 axially downward,thereby allowing the primary seal 735 to move radially outward, as shownon FIG. 7A.

FIG. 8 illustrates an alternative embodiment of a rotating control head800 in accord with the present invention. The rotating control head 800is constructed from similar components as the rotating control head 100,as shown on FIG. 1. Therefore, for convenience, similar components thatfunction in the same manner will be labeled with the same numbers as therotating control head 100. The primary difference between the rotatingcontrol head 800 and rotating control head 100 is the location of theactive seal assembly 105 and the passive seal assembly 110.

As shown in FIG. 8, the passive seal assembly 110 is disposed above theactive seal assembly 105. The passive seal assembly 110 is operativelyattached to the bladder support housing 135, thereby allowing thepassive seal assembly 110 to rotate with the active seal assembly 105.The passive seal assembly 110 is constructed and arranged in an axiallydownward conical shape, thereby allowing the pressure in the rotatingcontrol head 800 to act against the tapered surface 195 and close thepassive seal assembly 110 around the tubular (not shown). Additionally,the passive seal assembly 110 includes the inner diameter 190, which issmaller than the outer diameter of the tubular to allow an interferencefit between the tubular and the passive seal assembly 110.

As depicted, the active seal assembly 105 includes the bladder supporthousing 135 mounted on the plurality of bearings 125. The bladdersupport housing 135 is used to mount bladder 130. Under hydraulicpressure, bladder 130 moves radially inward to seal around a tubularsuch as a drilling tubular (not shown). Generally, fluid is supplied tothe chamber 150 under a controlled pressure to energize the bladder 130.Essentially, a hydraulic control (not shown) maintains and monitorshydraulic pressure within pressure chamber 150. Hydraulic pressure P1 ispreferably maintained by the hydraulic control between 0 to 200 psiabove a wellbore pressure P2. The bladder 130 is constructed fromflexible material allowing bladder surface 175 to press against thetubular at approximately the same pressure as the hydraulic pressure P1.

The hydraulic control may be used to de-energize the bladder 130 andallow the active seal assembly 105 to release the seal around thetubular. Generally, the fluid in the chamber 150 is drained into ahydraulic reservoir (not shown), thereby reducing the pressure P1.Subsequently, the bladder surface 175 loses contact with the tubular asthe bladder 130 becomes de-energized and moves radially outward. In thismanner, the seal around the tubular is released allowing the tubular tobe removed from the rotating control head 800.

FIG. 9 illustrates another alternative embodiment of a rotating controlhead, generally indicated at 900. The rotating control head 900 isgenerally constructed from similar components as the rotating controlhead 100, as shown in FIG. 1. Therefore, for convenience, similarcomponents that function in the same manner will be labeled with thesame numbers as the rotating control head 100. The primary differencebetween rotating control head 900 and rotating control head 100 is theuse of two passive seal assemblies 110, an alternative cooling systemusing one fluid to cool the radial seals and bearings in combinationwith a radial seal pressure protection system, and a secondary piston SPin addition to a primary piston P for urging the piston P to theunlatched position. These differences will be discussed below in detail.

While FIG. 9 shows the rotating control head 900 latched in a housing Habove a diverter D, it is contemplated that the rotating control headsas shown in the figures could be positioned with any housing or riser asdisclosed in U.S. Pat. Nos. 6,138,774, 6,263,982, 6,470,975, U.S. patentapplication Ser. No. 10/281,534, filed Oct. 28, 2002 and published Jun.12, 2003 under U.S. Patent Application No. 2003-0106712-A1, or U.S.patent application Ser. No. 10/995,980, filed Nov. 23, 2004, all ofwhich are assigned to the assignee of the present invention andincorporated herein by reference for all purposes.

As shown in FIG. 9, both passive seal assemblies 110 are operablyattached to the inner member support housing 135, thereby allowing thepassive seal assemblies to rotate together. The passive seal assembliesare constructed and arranged in an axially-downward conical shape,thereby allowing the wellbore pressure P2 in the rotating control head900 to act against the tapered surfaces 195 to close the passive sealassemblies around the tubular T. Additionally, the passive sealassemblies include inner diameters which are smaller than the outerdiameter of the tubular T to allow an interference fit between thetubular and the passive seal assemblies.

FIG. 11 discloses a cooling system where air enters a passageway, formedas a labyrinth L, in a rotating control head RCH similar to thepassageway shown in FIGS. 2A and 2B of the present invention.

FIG. 12 discloses a cooling system where hydraulic fluid moving throughinlet I to outlet O is used to cool the top radial seals S1 and S2 witha seal carrier in a rotating control head RCH.

Turning now to FIGS. 9, 13 and 14, the rotating control head 900 iscooled by a heat exchanger, generally indicated at 905. As best shown inFIGS. 13 and 14, heat exchanger 905 is constructed and arranged toremove heat from the rotating control head 900 using a fluid, such as anunctuous combustible substance. One such unctuous combustible substanceis a hydraulic oil, such as Mobil 630 ISO 90 weight oil. This fluid isintroduced at a low temperature into inlet 965, thereafter transferringheat from upper top radial seal 975A and lower top radial seal 975B, viaseal carrier 982A and its thermal transfer surfaces 982A′ and aplurality of bearings, including bearings 955, to the fluid as the fluidpasses through the heat exchanger 905 and, as best shown in FIG. 14, tooutlet 970.

In particular, the top radial seals 975A and 975B are cooled bycirculating the hydraulic fluid, preferably oil, in and out of thebearing section B and making multiple passes around the seals 975A and975B through a continuous spiral slot 980C in the seal housing 982B, asbest shown in FIGS. 9, 13 and 14. Since the hydraulic fluid that passesthrough slot passageway or slot 980C is the same fluid used to pressurethe bearing section B, the fluid can be circulated close to and with theradial seals 975A and 975B to improve the heat transfer properties.Although the illustrated embodiment uses a continuous spiral slot, otherembodiments are contemplated for different methods for making multiplepasses with one fluid adjacent to and in fluid contact with the radialseals.

As best shown in FIG. 14, the passageway of the heat exchanger 905includes inlet passageway 980A, outlet passageway 980B, and slotpassageway 980C that spirals between the lower portion of inletpassageway 980A to upper outlet passageway 980B. These multiple passesadjacent the radial seals 975A and 975B maximize the surface areacovered by the heat exchanger 905. The temperature hydraulic oilentering the inlet 965 flows through the passageway in the directionillustrated by arrows 985. As the oil circulates through the passageway,the oil increases in temperature as the heat from the rotating controlhead 900 is transferred to the oil. The higher temperature oil exits theoutlet 970. In this manner, the heat generated about the top radialseals in the rotating control head 900 is transferred to the oil passingthrough the multiple pass heat exchanger 905. Moreover, separate fluidsare not used to cool and to lubricate the rotating control head 900.Instead, only one fluid, such as a Mobil 630 ISO fluid 90 weight oil, isused to both cool and lubricate the rotating control head 900.

Returning to FIG. 9, it is contemplated that a similar cooling systemusing the multiple pass heat exchanger of the present invention could beused to cool the bottom radial seals 975C and 975D of the rotatingcontrol head 900.

Returning now to FIG. 13, the top radial seals 975A and 975B are stagedin tandem or series. The lower top radial seal 975B, which would becloser to the bearings 955, is a high flow seal that would allowapproximately two gallons of oil per minute to pass by seal 975B. Theupper top radial seal 975A, which would be the seal closer to theatmosphere or environment, would be a low flow seal that would allowapproximately 1 cc of oil per hour to pass by the seal 975A. A port 984,accessible from the atmosphere, is formed between the radial seals 975Aand 975B. As illustrated in both FIGS. 13 and 15B, anelectronically-controlled valve, generally indicated at V200, wouldregulate the pressure between the radial seals 975A and 975B.Preferably, as discussed below in detail, the pressure on upper topradial seal 975A is approximately half the pressure on lower top radialseal 975B so that the differential pressure on each radial seal islower, which in turn reduces the PV factor by approximately half.Testing of a Weatherford model 7800 rotating control head has shown thatwhen using a Kalsi seal, with part number 381-6-11, for the upper topradial seal 975A, and a modified (as discussed below) Kalsi seal, withpart number 432-32-10CCW (cutting and gluing), for the lower top radialseal 975B, has shown increased seal life of the top radial seals.

The Kalsi seals referred to herein can be obtained from KalsiEngineering, Inc. of Sugar Land, Tex. The preferred Kalsi 381-6-11 sealis stated by Kalsi Engineering, Inc. to have a nominal inside diameterof 10½″, a seal radial depth of 0.415″±0.008″, a seal axial width of0.300″, a gland depth of 0.380″, a gland width of 0.342″ and anapproximate as-molded seal inside diameter of 10.500″ (266.7 mm). Thisseal is further stated by Kalsi to be fabricated from HSN (peroxidecured, high ACN) with a material hardness of Shore A durometer of 85 to90. While the preferred Kalsi 432-32-10CCW seal is stated by KalsiEngineering, Inc. to have a nominal inside diameter of 42.375″, a sealradial depth of 0.460″±0.007″, a seal axial width of 0.300″, a glandwidth of 0.342″ and an approximate as-molded seal inside diameter of42.375″ (1,076 mm), this high flow seal was reduced to an insidediameter the same as the preferred Kalsi 381-6-11 seal, i.e. 10½″. Thishigh flow seal 975B is further stated by Kalsi to be fabricated from HSN(fully saturated peroxide cured, medium-high ACN) with a materialhardness of Shore A durometer of 85±5. It is contemplated that othersimilar sizes and types of manufacturers' seals, such as seals providedby Parker Hannifin of Cleveland, Ohio, could be used.

Startup Operation

Turning now to FIGS. 15A to 25 along with below Tables 1 and 2, thestartup operation of the hydraulic or fluid control of the rotatingcontrol head 900 is described. Referring particularly to FIG. 25, tostart the power unit, button PB10 on the control console, generallyindicated at CC, is pressed and switch SW10 is moved to the ON position.As discussed in the flowcharts of FIGS. 16-17, the program of theprogrammable logic controller PLC checks to make sure that button PB10and switch SW10 were operated less than 3 seconds of each other. If theelapsed time is equal to or over 3 seconds, the change in position ofSW10 is not recognized. Continuing on the flowchart of FIG. 16, the twotemperature switches TS10 and TS20, also shown in FIG. 15B, are thenchecked. These temperature switches indicate oil tank temperature. Whenthe oil temperature is below a designated temperature, e.g. 80° F., theheater HT10 (FIG. 15B) is turned on and the power unit will not beallowed to start until the oil temperature reaches the designatedtemperature. When the oil temperature is above a designated temperature,e.g. 130° F., the heater is turned off and cooler motor M2 is turned on.As described in the flowchart of FIG. 17, the last start up sequence isto check to see if the cooler motor M2 needs to be turned on.

Continuing on the flowchart of FIG. 16, the wellbore pressure P2 ischecked to see if below 50 psi. As shown in below Table 2, associatedalarms 10, 20, 30 and 40, light LT100 on control console CC, horn HN10in FIG. 15B, and corresponding text messages on display monitor DM onconsole CC will be activated as appropriate. Wellbore pressure P2 ismeasured by pressure transducer PT70 (FIG. 15A). Further, reviewingFIGS. 15B to 17, when the power unit for the rotating control head, suchas a Weatherford model 7800, is started, the three oil tank levelswitches LS10, LS20 and LS30 are checked. The level switches arepositioned to indicate when the tank 634 is overfull (no room for heatexpansion of the oil), when the tank is low (oil heater coil is close tobeing exposed), or when the tank is empty (oil heater coil is exposed).As long as the tank 634 is not overfull or empty, the power unit willpass this check by the PLC program.

Assuming that the power unit is within the above parameters, valves V80and V90 are placed in their open positions, as shown in FIG. 15B. Thesevalve openings unload gear pumps P2 and P3, respectively, so that whenmotor M1 starts, the oil is bypassed to tank 634. Valve V150 is alsoplaced in its open position, as shown in FIG. 15A, so that any otherfluid in the system can circulate back to tank 634. Returning to FIG.15B, pump P1, which is powered by motor M1, will compensate to apredetermined value. The pressure recommended by the pump manufacturerfor internal pump lubrication is approximately 300 psi. The compensationof the pump P1 is controlled by valve V10 (FIG. 15B).

Continuing review of the flowchart of FIG. 16, fluid level readingsoutside of the allowed values will activate alarms 50, 60 or 70 (seealso below Table 2 for alarms) and their respective lights LT100, LT50and LT60. Text messages corresponding to these alarms are displayed ondisplay monitor DM.

When the PLC program has checked all of the above parameters the powerunit will be allowed to start. Referring to the control console CC inFIG. 25, the light LT10 is then turned on to indicate the PUMP ON statusof the power unit. Pressure gauge PG20 on console CC continues to readthe pump pressure provided by pressure transducer PT10, shown in FIG.15B.

When shutdown of the unit desired, the PLC program checks to see ifconditions are acceptable to turn the power unit off. For example, thewellbore pressure P2 should be below 50 psi. Both the enable button PB10must be pressed and the power switch SW10 must be turned to the OFFposition within 3 seconds to turn the power unit off.

Latching Operation System Circuit

Closing the Latching System

Focusing now on FIGS. 9, 15A, 18, 23 and 24, the retainer member LP ofthe latching system of housing H is closed or latched, as shown in FIG.9, by valve V60 (FIG. 15A) changing to a flow position, so that theports P-A, B-T are connected. The fluid pilot valve V110 (FIG. 15A)opens so that the fluid on that side of the primary piston P can go backto tank 634 via line FM40L through the B-T port. Valve V100 preventsreverse flow in case of a loss of pressure. Accumulator A (which allowsroom for heat expansion of the fluid in the latch assembly) is set at900 psi, slightly above the latch pressure 800 psi, so that it will notcharge. Fluid pilot valve V140 (FIG. 15A) opens so that fluid underneaththe secondary piston SP goes back to tank 634 via line FM50L and valveV130 is forced closed by the resulting fluid pressure. Valve V70 isshown in FIG. 15A in its center position where all ports (APBT blocked)are blocked to block flow in any line. The pump P1, shown in FIG. 15B,compensates to a predetermined pressure of approximately 800 psi.

The retainer member LP, primary piston P and secondary piston SP of thelatching system are mechanically illustrated in FIG. 9 (latching systemis in its closed or latched position), schematically shown in FIG. 15A,and their operations are described in the flowcharts in FIGS. 18, 23 and24. Alternative latching systems are disclosed in FIGS. 1 and 8 and inU.S. patent application Ser. No. 10/995,980, filed Nov. 23, 2004.

With the above described startup operation achieved, the hydraulicsswitch SW20 on the control console CC is turned to the ON position. Thisallows the pump P1 to compensate to the required pressure later in thePLC program. The bearing latch switch SW40 on console CC is then turnedto the CLOSED position. The program then follows the process outlined inthe CLOSED leg of SW40 described in the flowchart of FIG. 18. The pumpP1 adjusts to provide 800 psi and the valve positions are then set asdetailed above. As discussed below, the PLC program then compares theamount of fluid that flows through flow meters FM30, FM40 and FM50 toensure that the required amount of fluid to close or latch the latchingsystem goes through the flow meters. Lights LT20, LT30, LT60 and LT70 onconsole CC show the proper state of the latch. Pressure gauge PG20, asshown on the control console CC, continues to read the pressure frompressure transducer PT10 (FIG. 15B).

Primary Latching System Opening

Similar to the above latch closing process, the PLC program follows theOPEN leg of SW40 as discussed in the flowchart of FIG. 18 and then theOFF leg of SW50 of FIG. 18 to open or unlatch the latching system.Turning to FIG. 15A, prior to opening or unlatching the retainer memberLP of the latching system, pressure transducer PT70 checks the wellborepressure P2. If the PT70 reading is above a predetermined pressure(approximately 50 psi), the power unit will not allow the retainermember LP to open or unlatch. Three-way valve V70 (FIG. 15A) is again inthe APBT blocked position. Valve V60 shifts to flow position P-B andA-T. The fluid flows through valve V10 into the chamber to urge theprimary piston P to move to allow retainer member LP to unlatch. Thepump P1, shown in FIG. 15B, compensates to a predetermined value(approximately 2000 psi). Fluid pilots open valve V100 to allow fluid ofthe primary piston P to flow through line FM30L and the A-T ports backto tank 634.

Secondary Latching System Opening

The PLC program following the OPEN leg of SW40 and the OPEN leg of SW50,described in the flowchart of FIG. 18, moves the secondary piston SP.The secondary piston SP is used to open or unlatch the primary piston Pand, therefore, the retainer member LP of the latching system. Prior tounlatching the latching system, pressure transducer PT70 again checksthe wellbore pressure P2. If PT70 is reading above a predeterminedpressure (approximately 50 psi), the power unit will not allow thelatching system to open or unlatch. Valve V60 is in the APBT blockedposition, as shown in FIG. 15A. Valve V70 then shifts to flow positionP-A and B-T. Fluid flows to the chamber of the secondary latch piston SPvia line FM50L. With valve V140 forced closed by the resulting pressureand valve V130 piloted open, fluid from both sides of the primary pistonP is allowed to go back to tank 634 though the B-T ports of valve V70.

Bearing Assembly Circuit

Continuing to review FIGS. 9, 15A, 15B and 18 and the below Tables 1 and2, now review FIGS. 19 to 22 describing the bearing assembly circuit.

Valve positions on valve V80 and valve V90, shown in FIG. 15B, and valveV160, shown in FIG. 15A, are moved to provide a pressure in the rotatingcontrol head that is above the wellbore pressure P2. In particular, thewellbore pressure P2 is measured by pressure transducer PT70, shown inFIG. 15A. Depending on the wellbore pressure P2, valve V90 and valve V80(FIG. 15B) are either open or closed. By opening either valve, pressurein the rotating control head can be reduced by allowing fluid to go backto tank 634. Also, depending on pressure in the rotating control head,valve V160 will move to a position that selects a different sizeorifice. The orifice size, e.g. 3/32″ or ⅛″ (FIG. 15A), will determinehow much back pressure is in the rotating control head. By using thiscombination of valves V80, V90 and V160, four different pressures can beachieved.

During the operation of the bearing assembly circuit, the temperatureswitches TS10 and TS20, described in the above startup operation,continue to read the oil temperature in the tank 634, and operate theheater HT10 or cooler motor M2, as required. For example, if the oiltemperature exceeds a predetermined value, the cooler motor M2 is turnedon and the cooler will transfer heat from the oil returning from thebearing section or assembly B.

Flow meter FM10 measures the volume or flow rate of fluid or oil to thechamber in the bearing section or assembly B via line FM10L. Flow meterFM20 measures the volume or flow rate of fluid or oil from the chamberin the bearing section or assembly B via line FM20L. As discussedfurther below in the bearing leak detection system section, if the flowmeter FM20 reading is greater than the flow meter FM10 reading, thiscould indicate that wellbore fluid is entering the bearing assemblychamber. Valve V150 is then moved from the open position, as shown inFIG. 15A, to its closed position to keep the wellbore fluid from goingback to tank 634.

Regulating Pressure in the Radial Seals

Reviewing FIGS. 13, 14, 15B, 22 and 23 along with the below Tables 1 and2, pressure transducer PT80 (FIG. 15B) reads the amount of fluid “sealbleed” pressure between the top radial seals 975A and 975B via port 984.As discussed above, proportional relief valve V200 adjusts to maintain apredetermined pressure between the two radial seals 975A and 975B. Basedon the well pressure P2 indicated by the pressure transducer PT70, thevalve V200 adjusts to achieve the desired “seal bleed” pressure as shownin the below Table 1. TABLE 1 WELL PRESSURE SEAL BLEED PRESSURE   0-500100  500-1200 300 1200-UP 700

The flowchart of FIG. 18 on the CLOSED leg of SW40 and after thesubroutine to compare flow meters FM30, FM40 and FM50, describes how thevalves adjust to match the pressures in above Table 1. FIGS. 19 to 22describes a subroutine for the program to adjust pressures in relationto the wellbore pressure P2.

Alarms

During the running of the PLC program, certain sensors such as flowmeters and pressure transducers are checked. If the values are out oftolerance, alarms are activated. The flowcharts of FIGS. 16-18 describewhen the alarms are activated. Below Table 2 shows the lights, horn andcauses associated with the activated alarms. The lights listed in Table2 correspond to the lights shown on the control console CC of FIG. 25.As discussed below, a text message corresponding to the cause is sent tothe display monitor DM on the control console CC.

Latch Leak Detection System

FM30/FM40 Comparison

Usually the PLC program will run a comparison where the secondary pistonSP is “bottomed out” or in its latched position, such as shown in FIG.9, or when only a primary piston P is used, such as shown in FIG. 1, thepiston P is bottomed out. In this comparison, the flow meter FM30coupled to the line FM30L measures either the flow volume value or flowrate value of fluid to the piston chamber to move the piston P to thelatched position, as shown in FIG. 9, from the unlatched position, asshown in FIG. 1. Also, the flow meter FM40 coupled to the line FM40Lmeasures the desired flow volume value or flow rate value from thepiston chamber. Since the secondary piston SP is bottomed out, thereshould be no flow in line FM50L, as shown in FIG. 9. Since no secondarypiston is shown in FIG. 1, there is no line FM50L or flow meter FM50.

In this comparison, if there are no significant leaks, the flow volumevalue or flow rate value measured by flow meter FM30 should be equal tothe flow volume value or flow rate value, respectively, measured by flowmeter FM40 within a predetermined tolerance. If a leak is detectedbecause the comparison is outside the predetermined tolerance, theresults of this FM30/FM40 comparison would be displayed on displaymonitor DM on control console CC, as shown in FIG. 25, preferably in atext message, such as “Alarm 90—Fluid Leak”. Furthermore, if the valuesfrom flow meter FM30 and flow meter FM40 are not within thepredetermined tolerance, i.e. a leak is detected, the correspondinglight LT100 would be displayed on the control console CC.

FM30/FM50 Comparison

In a less common comparison, the secondary piston SP would be in its“full up” position. That is, the secondary piston SP has urged theprimary piston P, when viewing FIG. 9, as far up as it can move to itsfull unlatched position. In this comparison, the flow volume value orflow rate value, measured by flow meter FM30 coupled to line FM30L, tomove piston P to its latched position, as shown in FIG. 9, is measured.If the secondary piston SP is sized so that it would block line FM40L,no fluid would be measured by flow meter FM40. But fluid beneath thesecondary piston SP would be evacuated via line FM50L from the pistonchamber of the latch assembly. Flow meter 50 would then measure the flowvolume value or flow rate value. The measured flow volume value or flowrate value from flow meter FM30 is then compared to the measured flowvolume value or flow rate value from flow meter FM50.

If the compared FM30/FM50 values are within a predetermined tolerance,then no significant leaks are considered detected. If a leak isdetected, the results of this FM30/FM50 comparison would be displayed ondisplay monitor DM on control console CC, preferably in a text message,such as “Alarm 100—Fluid Leak”. Furthermore, if the values from flowmeter FM30 and flow meter FM50 are not within a predetermined tolerance,the corresponding light LT100 would be displayed on the control consoleCC.

FM30/FM40+FM50 Comparison

Sometimes the primary piston P is in its full unlatched position and thesecondary piston SP is somewhere between its bottomed out position andin contact with the fully unlatched piston P. In this comparison, theflow volume value or flow rate value measured by the flow meter FM30 tomove piston P to its latched position is measured. If the secondarypiston SP is sized so that it does not block line FM40L, fluid betweensecondary piston SP and piston P is evacuated by line FM40L. The flowmeter FM40 then measures the flow volume value or flow rate value vialine FM40L. This measured value from flow meter FM40 is compared to themeasured value from flow meter FM30. Also, the flow value beneathsecondary piston SP is evacuated via line FM50L and measured by flowmeter FM50.

If the flow value from flow meter FM30 is not within a predeterminedtolerance of the compared sum of the flow values from flow meter FM40and flow meter FM50, then the corresponding light LT100 would bedisplayed on the control console CC. This detected leak is displayed ondisplay monitor DM in a text message.

Measured Value/Predetermined Value

An alternative to the above leak detection methods of comparing measuredvalues is to use a predetermined or previously calculated value. The PLCprogram then compares the measured flow value in and/or from thelatching system to the predetermined flow value plus a predeterminedtolerance.

It is noted that in addition to indicating the latch position, the flowmeters FM30, FM40 and FM50 are also monitored so that if fluid flowcontinues after the piston P has moved to the closed or latched positionfor a predetermined time period, a possible hose or seal leak isflagged.

For example, alarms 90, 100 and 110, as shown in below Table 2, could beactivated as follows:

Alarm 90—primary piston P is in the open or unlatched position. The flowmeter FM40 measured flow value is compared to a predetermined value plusa tolerance to indicate the position of piston P. When the flow meterFM40 reaches the tolerance range of this predetermined value, the pistonP is indicated in the open or unlatched position. If the flow meter FM40either exceeds this tolerance range of the predetermined value orcontinues to read a flow value after a predetermined time period, suchas an hour, the PLC program indicates the alarm 90 and its correspondinglight and text message as discussed herein.

Alarm 100—secondary piston SP is in the open or unlatched position. Theflow meter FM50 measured flow value is compared to a predetermined valueplus a tolerance to indicate the position of secondary piston SP. Whenthe flow meter FM50 reaches the tolerance range of this predeterminedvalue, the secondary piston SP is indicated in the open or unlatchedposition. If the flow meter FM50 either exceeds this tolerance range ofthe predetermined value or continues to read a flow value after apredetermined time period, such as an hour, the PLC program indicatesthe alarm 100 and its corresponding light and text message as discussedherein.

Alarm 110—primary piston P is in the closed or latched position. Theflow meter FM30 measured flow value is compared to a predetermined valueplus a tolerance to indicate the position of primary piston P. When theflow meter FM30 reaches the tolerance range of this predetermined value,the primary piston P is indicated in the closed or latched position. Ifthe flow meter FM30 either exceeds this tolerance range of thepredetermined value or continues to read a flow value after apredetermined time period, such as an hour, the PLC program indicatesthe alarm 110 and its corresponding light and text message as discussedherein.

Bearing Leak Detection System

FM10/FM20 Comparison

A leak detection system can also be used to determine if the bearingsection or assembly B is losing fluid, such as oil, or, as discussedabove, gaining fluid, such as wellbore fluids. As shown in FIG. 15A,line FM10L and line FM20L move fluid to and from the bearing assembly Bof a rotating control head and are coupled to respective flow metersFM10 and FM20.

If the measured fluid value, such as fluid volume value or fluid ratevalue, from flow meter FM10 is not within a predetermined tolerance ofthe measured fluid value from flow meter FM20, then alarms 120, 130 or140, as described below in Table 2, are activated. For example, if themeasured flow value to the bearing assembly B is greater than themeasured flow value from the bearing assembly plus a predeterminedpercentage tolerance, then alarm 120 is activated and light LT90 oncontrol console CC is turned on. Also, a text message is displayed ondisplay monitor DM on the control console CC, such as “Alarm 120—LosingOil.” For example, this loss could be from the top radial seals leakingoil to the atmosphere, or the bottom radial seals leaking oil down thewellbore.

If the measured flow value from the bearing assembly read by flow meterFM20 is greater than the measured flow value to the bearing assemblyread by flow meter FM10 plus a predetermined percentage tolerance, thenalarm 130 is activated, light LT90 is turned on and a text message suchas “Alarm 130—Gaining Oil” is displayed on display monitor DM.

If the measured flow meter FM20 flow value/measured flow meter FM10 flowvalue is higher than the alarm 130 predetermined percentage tolerance,then alarm 140 is activated, light LT90 is turned on and a horn soundsin addition to a text message on display monitor DM, such as “Alarm140—Gaining Oil.”

An alternative to the above leak detection methods of comparing measuredvalues is to use a predetermined or previously calculated value. The PLCprogram then compares the measured flow value in and/or from the bearingassembly B to the predetermined flow value plus a predeterminedtolerance. TABLE 2 ALARM # LIGHT HORN CAUSE 10 LT100 WB > 100 WELLBORE >50, PT10 = 0; NO LATCH PUMP PRESSURE 20 LT100 WB > 100 WELLBORE > 50,PT20 = 0; NO BEARING LUBE PRESSURE 30 LT100 Y WELLBORE > 50, LT20 = OFF;LATCH NOT CLOSED 40 LT100 Y WELLBORE > 50, LT30 = OFF; SECONDARY LATCHNOT CLOSED 50 LT100 LS30 = ON; TANK OVERFULL 60 LT50 LS20 = OFF; TANKLOW 70 LT50 Y LS10 = OFF; TANK EMPTY 80 LT100 Y WELLBORE > 100, PT10 =0; NO LATCH PRESSURE 90 LT100 FM40; FLUID LEAK; 10% TOLERANCE + FLUIDMEASURE 100 LT100 FM50; FLUID LEAK; 10% TOLERANCE + FLUID MEASURE 110LT100 FM30; FLUID LEAK; 10% TOLERANCE + FLUID MEASURE 120 LT90 FM10 >FM20 + 25%; BEARING LEAK (LOSING OIL) 130 LT90 FM20 > FM10 + 15%;BEARING LEAK (GAINING OIL) 140 LT90 Y FM20 > FM10 + 30%; BEARING LEAK(GAINING OIL)Piston Position Indicators

Additional methods are contemplated to indicate position of the primarypiston P and/or secondary piston SP in the latching system. One examplewould be to use an electrical sensor, such as a linear displacementtransducer, to measure the distance the selected piston has moved.

Another method could be drilling the housing of the latch assembly for avalve that would be opened or closed by either the primary piston P, asshown in the embodiment of FIG. 1, or the secondary piston SP, as shownin the embodiment of FIGS. 9, 26 and 27. In this method, a port PO wouldbe drilled or formed in the bottom of the piston chamber of the latchassembly. Port PO is in fluid communication with an inlet port IN (FIG.26) and an outlet port OU (FIG. 27) extending perpendicular (radiallyoutward) from the piston chamber of the latch assembly. Theseperpendicular ports would communicate with respective passages INP andOUP that extend upward in the radially outward portion of the latchassembly housing. Housing passage OUP is connected by a hose to apressure transducer and/or flow meter. A machined valve seat VS in theport to the piston chamber receives a corresponding valve seat, such asa needle valve seat. The needle valve seat would be fixedly connected toa rod R receiving a coil spring CS about its lower portion to urge theneedle valve seat to the open or unlatched position if neither primarypiston P (FIG. 1 embodiment) nor secondary piston SP (FIGS. 9, 26 and 27embodiments) moves the needle valve seat to the closed or latchedposition. An alignment retainer member AR is sealed as the member isthreadably connected to the housing H. The upper portion of rod R isslidably sealed with retainer member AR.

If a flow value and/or pressure is detected in the respective flow meterand/or pressure transducer communicating with passage OUP, then thevalve is indicated open. This open valve indicates the piston is in theopen or unlatched position. If no flow value and/or pressure is detectedin the respective flow meter and/or pressure transducer communicatingwith passage OUP, then the valve is indicated closed. This closed valveindicates the piston is in the closed or latched position. The abovepiston position would be shown on the console CC, as shown in FIG. 25,by lights LT20 or LT60 and LT30 or LT70 along with a corresponding textmessage on display monitor DM.

While the foregoing is directed to embodiments of the present invention,other and further embodiments of the invention may be devised withoutdeparting from the basic scope thereof, and the scope thereof isdetermined by the claims that follow.

1. A thermal transfer system adapted for use with a rotating controlhead, comprising: a first member movable relative to a second member;one of the members having a thermal transfer surface; a first sealpositioned with one of the members for sealing the first member and thesecond member while the first member moves relative to the secondmember; a thermal transfer fluid circulated with at least one of themembers; and the thermal transfer surface transferring thermal unitsthrough multiple passes of the thermal transfer fluid adjacent theterminal transfer surface.
 2. The system of claim 1 further comprising:the thermal transfer surface comprises a surface of a seal carrier; theseal carrier disposed with one of the members; and the first sealpositioned with the seal carrier for sealing the first member with thesecond member while the first member moves relative to the secondmember.
 3. The system of claim 1, wherein the multiple passes comprise:a spiral slot formed on one of the members adjacent the thermal transfersurface.
 4. The system of claim 2, wherein the multiple passes comprise:a spiral slot formed on one of the members adjacent the thermal transfersurface.
 5. The system of claim 3 wherein the spiral slot provides acontinuous flow passageway for the thermal transfer fluid.
 6. The systemof claim 4 wherein the spiral slot provides a continuous flow passagewayfor the thermal transfer fluid.
 7. The system of claim 1 furthercomprising: at least one bearing provided between the first member andthe second member.
 8. The system of claim 7 wherein the thermal transferfluid is pressurized and communicates with the bearing.
 9. The system ofclaim 1 wherein the thermal transfer fluid is an unctuous combustiblesubstance that is at least liquefiable on warming.
 10. The system ofclaim 7 further comprising a tubular wherein one of the members having abore sized to receive the tubular.
 11. The system of claim 7 wherein theat least one bearing comprising: a radial bearing, and a thrust bearing.12. The system of claim 1 further comprising a port formed in one of themembers to communicate with the first seal and to regulate the pressureof the fluid on the first seal.
 13. The system of claim 1 furthercomprising a second seal positioned with one of the members and forsealing the first member and the second member.
 14. The system of claim13 further comprising a port formed in one of the members to communicatewith the first seal and the second seal and to regulate the pressure ofthe fluid between the first seal and the second seal.
 15. The system ofclaim 13 further comprising the first seal allowing a firstpredetermined flow of the thermal transfer fluid to pass by the firstseal, and the second seal allowing a second predetermined flow of thethermal transfer fluid to pass by the second seal and the secondpredetermined flow is greater than the first predetermined flow.
 16. Thesystem of claim 13 wherein one of the seals allows flow of fluid at afirst predetermined pressure and the other seal allows flow of fluid ata second predetermined pressure, the first predetermined pressure ishigher than the second predetermined pressure.
 17. The system of claim 2further comprising a port formed in the seal carrier to communicate withthe first seal and to regulate the pressure of the fluid on the firstseal.
 18. The system of claim 2 further comprising a second sealpositioned with the seal carrier and for sealing the first member andthe second member.
 19. The system of claim 18 further comprising a portformed in the seal carrier to communicate with the first seal and thesecond seal and to regulate the pressure of the fluid between the firstseal and the second seal.
 20. The system of claim 18 further comprisingthe first seal allowing a first predetermined flow of the thermaltransfer fluid to pass by the first seal, and the second seal allowing asecond predetermined flow of the thermal transfer fluid to pass by thesecond seal and the second predetermined flow is greater than the firstpredetermined flow.
 21. The system of claim 18 wherein one of the sealsallows flow of fluid at a first predetermined pressure and the otherseal allows flow of fluid at a second predetermined pressure, the firstpredetermined pressure is higher than the second predetermined pressure.22. A system adapted for use with a rotating control head, comprising: afirst member movable relative to a second member; a fluid circulatedwith at least one of the members; a first seal positioned with one ofthe members for providing a predetermined flow value of the fluidbetween the first member and the second member; and a port formed in oneof the members, the port communicating with the first seal to regulatethe fluid flowing by the first seal.
 23. The system of claim 22 furthercomprising a second seal positioned with the first member and the secondmember, wherein one of the seals allows flow of fluid at a firstpredetermined pressure and the other seal allows flow of fluid at asecond predetermined pressure.
 24. The system of claim 22 furthercomprising a second seal positioned with the first member and the secondmember, wherein the first seal allowing a first predetermined flow ofthe fluid to pass by the first seal, and the second seal allowing asecond predetermined flow of the fluid to pass by the second seal andthe second predetermined flow is different than the first predeterminedflow.
 25. A thermal transfer system adapted for use with a rotatingcontrol head, comprising: a first member movable relative to a secondmember; one of the members having a thermal transfer surface; a firstseal positioned with one of the members for sealing the first memberwith the second member while the first member moves relative to thesecond member; a second seal positioned with one of the members forsealing the first member with the second member wherein the first sealallows flow of fluid at a first predetermined pressure and the secondseal allows flow of fluid at a second predetermined pressure differentthan the first predetermined pressure; a thermal transfer fluidcirculated with at least one of the members; and the thermal transfersurface transferring thermal units through multiple passes of thethermal transfer fluid adjacent the thermal transfer surface.
 26. Thesystem of claim 25, wherein the multiple passes comprises a spiral slotformed on one of the members adjacent the thermal transfer surface. 27.A method for cooling a first radial seal in a rotating control head,comprising: passing a cooling medium through the rotating control headwith multiple passes adjacent to the first radial seal; and regulatingthe pressure of the cooling medium on the first radial seal.
 28. Themethod of claim 27, further comprising the step of: spiraling thecooling medium about the first radial seal in the rotating control head.29. The method of claim 27, wherein the cooling medium is an unctuouscombustible substance that is at least liquefiable on warming.
 30. Themethod of claim 27 further comprising a second radial seal and furthercomprising the step of: sealing between a first member that movesrelative to the second member in the rotating control head with thefirst radial seal and the second radial seal.
 31. The method of claim 30further comprising the step of: regulating the pressure between thefirst radial seal and the second radial seal.
 32. The method of claim 30further comprising the step of: allowing flow of fluid pass the secondradial seal at a higher rate than the flow of fluid pass the firstradial seal.
 33. A system, comprising: a latch assembly comprising afirst piston movable between a latched position and an unlatchedposition; a comparator configured to compare a fluid value moving to andfrom the latch assembly; and wherein the latch assembly is remotelyactuatable.
 34. The system of claim 33, further comprising: a rotatingcontrol head, wherein the rotating control head is latched to the latchassembly when the first piston is in the latched position.
 35. Thesystem of claim 34, the latch assembly further comprising: a housingforming a chamber, wherein the first piston is positioned within thechamber.
 36. The system of claim 33, wherein the first piston ishydraulically actuated by the fluid to move between the latched positionand the unlatched position.
 37. The system of claim 33, furthercomprising: a first fluid line operatively connected to the latchassembly for delivering the fluid to the latch assembly; a first metercoupled to the first fluid line, the first meter measuring a first fluidvolume value for fluid delivered to the latch assembly; a second fluidline operatively connected to the latch assembly for communicating thefluid from the latch assembly; a second meter coupled to the secondfluid line, the second meter measuring a second fluid volume value forfluid from the latch assembly; the comparator configured to compare themeasured first fluid volume value to the measured second fluid volumevalue; and a display coupled to the comparator.
 38. The system of claim37, wherein the display indicates the results of the comparison of themeasured first fluid volume value relative to the measured second fluidvolume value.
 39. The system of claim 37, the display comprising a textmessage.
 40. A comparator system for use with a latching assembly tolatch a rotating control head, comprising: a first fluid lineoperatively connected to the latch assembly for delivering a fluid tothe latch assembly; a first meter coupled to the first line, the firstmeter measuring a first fluid value for fluid delivered to the latchassembly; a second fluid line operatively connected to the latchassembly for communicating the fluid from the latch assembly; a secondmeter coupled to the second fluid line, the second meter measuring asecond fluid value for fluid from the latch assembly; a comparatorconfigured to compare the measured first fluid value to the second fluidvalue; and a display coupled to the comparator.
 41. The system of claim40, wherein the display indicates the results of the comparison of thefirst measured fluid value to the second fluid value.
 42. A comparatorsystem for use with a bearing assembly of a rotating control head,comprising: a first fluid line operatively coupled to communicate fluidto a chamber defined by the bearing assembly; a first meter coupled tothe first fluid line, the first meter measuring a first fluid value; asecond fluid line operatively coupled to communicate fluid from thechamber defined by the bearing assembly; a second meter coupled to thesecond fluid line, the second meter measuring a second fluid value; acomparator, coupled to the first meter and the second meter, configuredto compare the measured first fluid value to the measured second fluidvalue; and a display coupled to the comparator.
 43. The system of claim42, wherein the measured first fluid value is a measured fluid volumevalue for fluid delivered to the chamber, and wherein the measuredsecond fluid value is a measured second fluid volume value.
 44. Thesystem of claim 43, wherein the results of the compared measured firstfluid volume value and the measured second fluid volume value isdisplayed on the display.
 45. The system of claim 42, wherein themeasured first fluid value is a measured fluid flow rate value, andwherein the measured second fluid value is a measured second fluid flowrate value.
 46. The system of claim 42, wherein the display indicates atext message resulting from the compared measured first fluid value tothe measured second fluid value.
 47. A system, comprising: a rotatingcontrol head; a latch assembly, latchable to the rotating control head,comprising: a retainer member, radially movable between an unlatchedposition and a latched position, the retainer member latched with therotating control head in the latched position; and a piston having afirst side and a second side, movable between a first position and asecond position, the piston urging the retainer member to move to thelatched position when the piston is in the first position and the firstpiston allowing the retainer member to move to the unlatched positionwhen the piston is in the second position; a comparator system, remotelycoupled to the latch assembly, comprising: a first fluid lineoperatively coupled to communicate fluid to a chamber for receiving thepiston; a first meter coupled to the first fluid line, the first metermeasuring a first fluid value; a second fluid line operatively coupledto communicate fluid from the chamber for receiving the piston; a secondmeter coupled to the second fluid line, the second meter measuring asecond fluid value; a comparator, coupled to the first meter and thesecond meter, configured to compare the measured first fluid value tothe measured second fluid value; and a display coupled to thecomparator.
 48. The system of claim 47, wherein the measured first fluidvalue is a measured fluid volume value for fluid delivered to thechamber on one side of the piston, and the measured second fluid valueis a measured fluid volume value for fluid from the chamber on the otherside of the piston.
 49. The system of claim 48, wherein the comparedmeasured first fluid volume value and the measured second fluid volumevalue is displayed on the display.
 50. The system of claim 47, whereinthe first measured first fluid value is a measured fluid flow ratevalue, and the measured second fluid value is a measured second fluidflow rate value.
 51. A method for comparing fluid to and from a latchassembly for latching a rotating control head, comprising the steps of:delivering a fluid to a first side of a piston for moving the pistonfrom a first position to a second position; measuring a volume of fluiddelivered to the first side of the piston producing a measured firstfluid volume value; communicating the fluid from a second side of thepiston; measuring a volume of fluid from the second side of the pistonproducing a measured second fluid volume value; and comparing themeasured first fluid volume value to a measured second fluid volumevalue.
 52. The method of claim 51, the steps of measuring a volume offluid comprising: measuring the fluid with a totalizing flow meter;reading the totalizing flow meter, producing the measured fluid volumevalue.
 53. A method for use of a rotating control head having a bearingassembly for rotating while drilling, comprising the steps of:positioning a chamber in the bearing assembly; forming a first openinginto the chamber; forming a second opening into the chamber; deliveringa fluid to the first opening; communicating the fluid from the secondopening; measuring a flow value of the fluid to the first opening;measuring a flow value of the fluid from the second opening; andcomparing the measured flow value to the first opening to the measuredflow value from the second opening.
 54. The method of claim 53, thesteps of measuring a flow value of the fluid to the first openingcomprising: measuring the flow rate to the first opening with a firstflow meter; and reading the first flow meter and producing a measuredfirst flow rate value.
 55. The method of claim 54, the step of measuringa flow value of the fluid to the first opening comprising: measuring theflow rate from the second opening with a first flow meter; and readingthe first flow meter and producing a measured first flow rate value. 56.The method of claim 55, further comprising the steps of comparing themeasured first flow rate value to the first opening to the measuredsecond flow rate from the second opening.
 57. The method of claim 53,the step of measuring a flow value of the fluid to the first openingcomprising: measuring the flow volume with a first flow meter; andreading the first flow meter and producing a measured first flow volumevalue.
 58. The method of claim 57, the step of measuring a flow value ofthe fluid from the second opening comprising: measuring the flow volumewith a second flow meter; and reading the second flow meter andproducing a measured second flow volume value.
 59. The method of claim58, further comprising the step of comparing the measured first flowvolume value to the measured second flow volume.